The Duchess of Cambridge is planning to spend her 31st birthday today quietly and privately.

St James' Palace confirmed that Kate - who is around 12 weeks pregnant - will mark the occasion in a low-key fashion.

The Duchess is expected to spend the day with her husband at their home in Anglesey, North Wales.

It was recently claimed that William plans to buy Kate a country estate as a birthday gift so they have a retreat out of the city after they move into their apartment in Kensington Palace.

A source said: "They've talked about getting a place where they can get away from it all. And now William has narrowed down the list to a few incredible places in Hampshire and Buckinghamshire around the £5 million mark. They don't want to be too close to London as they are already based in Kensington Palace.

"William has gathered together various property details from some high-end retail estates which he will give to her on her birthday on January 9."

It also emerged today that the Duchess is planning to wear looser clothes during her pregnancy to avoid the "bottom situation" suffered by her sister Pippa.

Designer Roland Mouret - who has dressed Kate on several occasions - said: "She's highly attuned to those details that will provoke a tabloid frenzy, and above all, she does not want a tabloid frenzy.

"She doesn't seem to feel the need to dress sexily to woo the world. She's dressing for William and herself. She doesn't want a bottom situation like Pippa had."

Mouret also claims the Duchess has less fashion power than Kim Kardashian.

He told Vogue magazine: "You don't see hundreds of women running around looking like Kate.

"The kind of people who like Kate's style are not the kind to rush out and copy her dress. To be honest, we're more likely to get orders on a dress that Kim Kardashian's worn."